torsdag 15 mars 2012

What Is The "Greenhouse Effect"?

In recent posts I have documented a discussion with Roy Spencer and Fred Singer on "backradiation" and the "greenhouse effect" connecting to an exchange between Pierre Latour and Richard Lindzen with the following summary by Lindzen:

This rather bizarre 'discourse' seems to centered on the fact that the greenhouse effect that you are criticizing is essentially the one presented by Gore and possibly implicit in the Trenberth-Kiehl figure. This is not the greenhouse effect that Roy, Fred and I are talking about. The one we are talking about is the one that is actually working in all radiative convective calculations and in GCMs. Why don't you spend the little time needed to understand the difference?

The rather bizarre discourse illustrates the fact that the meaning of the "greenhouse effect" has many different definitions:

What makes the Earth’s surface warmer than it would otherwise be (e.g. Spencer).

The combined effect of all "greenhouse gases" water vapor, CO2,..= radiation alone.

The effect of doubled CO2 without feed-back according to Stefan-Boltzmann with assumed radiative forcing of 4 W/m2 = 1 C = definition of no-feedback climate sensitivity.

The real effect of doubled CO2 with feedback = anything between 0 C and 6 C.

Here, 5 is the relevant definition, which however in a discussion can freely be mixed up with any of 1-4. The information about 5 is meager: It can be anything from 0 C to an alarming overheating of up to 6 C, or even cooling.

Which "greenhouse effect" is it then Dick is speaking about together with Fred and Roy, which is not that of Gore and Kiehl-Trenberth, but the one "working in all radiative convective calculations and in GCMs" which give support to Gore's apocalypses??

In politics and religion it is important to not define basic terms clearly, but in science this is completely central in order to make the discussion meaningful. The following questions thus should be answered:

What is a scientific description of the "greenhouse effect"?

What are the (possible) effects of the "greenhouse effect"?

Can they be observed?

Have they been observed?

Numbers?

Here is a response to Pierre from Roy, which is I guess directed to me as well:

Pierre: Since Dick might be too polite to respond, I will.

When a scientist wants to learn what is known on a certain subject, he/she reads the pertinent literature. This is not easy, but it is also not our jobs to educate you on a difficult subject.

You could ask me to prove from first principles that force equals mass times acceleration (F=MA), but I am either going to ignore your request, or ask you to read the literature first.

Your requests waste everyone's time, and you seem to believe a lack of response means your views and criticisms have merit, when in fact they have too little merit to deserve a response.

If you want to play in this game and be taken seriously, do what scientists do...go do your homework first.

-Roy

This is a very a clever (not polite) answer, but it has nothing to do with science. I have the impression that alarmists play dirty games, but is it really necessary that also skeptics do the same. If you have science on your side you'd better play a fair game. Right, Roy?